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Growth and body composition, feed intake and carcass composition traits of developing gilts fed different dietary lysine and metabolizable energy levels
The objective of this study was to manipulate the lean:fat ratio of replacement gilts by feeding diets differing in lysine and metabolizable energy (ME) content. Crossbred Large White × Landrace gilts (n = 1221) were housed in groups of 17 to 18 gilts and randomly allotted at 100 d of age to receive one of 6 corn-soybean diets formulated to provide 2 standardized ileal digestible (SID) lysine and 3 ME levels. Gilts received grower diets formulated to provide 0.86% or 1.02% SID lysine and 2.94 (Low), 3.25 (Medium) or 3.57 (High) Mcal of ME/kg from 100 d of age until approximately 90 kg BW. Then, gilts were fed finisher diets containing 0.73% or 0.85% SID lysine and 2.94 (Low), 3.26 (Medium) or 3.59 Mcal (High) of ME/kg until 260 d of age. Gilts were weighed and backfat thickness and loin area were recorded at the beginning of the trial and then every 28 d. Feed intake was recorded as feed disappearance within the pen at 2 wk intervals. Lysine (g) and ME (Mcal) consumed were calculated based on diet formulations. Pen was considered the experimental unit (12 pens per diet; 72 pens on trial). Data were analyzed using a mixed model, which included lysine and ME content, data recording day, and their interactions as fixed effects. Body weight at 100 d of age was used as a linear covariate. Pen within lysine × ME level × barn was included as a random effect. There were no differences between lysine or ME levels or their interaction for growth and body composition, except for backfat, which was greater for gilts fed a High ME (~2 mm; P < 0.05). Gilts fed High ME diets consumed 14.7 kg and 7.6 kg less (P < 0.05) feed than gilts fed the Low ME and Medium ME diets, respectively. Gilts fed the High ME diet consumed 0.72 kg and 0.38 kg of feed and 5.7 g and 3 g of lysine less per kg of BW gain (P < 0.05) than gilts fed Low ME or Medium ME diets, respectively. Gilts consumed approximately 13 Mcal of ME/kg of BW gain irrespective of dietary treatment. Growth and body composition was not altered when provided with ad libitum access to diets differing in lysine and ME content as gilts displayed compensatory feed intake. These data suggest that SID lysine and ME requirements were met even for the lowest SID lysine and ME level provided.
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Keywords: Body composition, lysine, metabolizable energy